The beta-cells of the islets of Langerhans in the pancreas secrete insulin in response to factors such as amino acids, glyceraldehyde, free fatty acids, and, most prominently, glucose. The capacity of normal islet beta-cells to sense a rise in blood glucose concentration and to respond to elevated levels of glucose by secreting insulin is critical to the control of blood glucose levels. Increased insulin secretion in response to a glucose load prevents hyperglycemia in normal individuals by stimulating glucose uptake into peripheral tissues, particularly muscle and adipose tissue.
Individuals in whom islet beta-cells function is impaired suffer from diabetes. Insulin-dependent diabetes mellitus, or IDDM (also known as Juvenile-onset or Type I diabetes), represents approximately 10% of all human diabetes. IDDM is distinct from non-insulin dependent diabetes (NIDDM) in that only IDDM involves specific destruction of the insulin producing beta-cells of the islets of Langerhans. The destruction of beta-cells in IDDM appears to be a result of specific autoimmune attack, in which the patient's own immune system recognizes and destroys the beta-cells, but not the surrounding alpha-cells (glucagon producing) or delta-cells (somatostatin producing) that comprise the islet.
Treatment options for IDDM are centered on self-injection of insulin—an inconvenient and imprecise solution—and thus the development of new therapeutic strategies is highly desirable. The possibility of islet or pancreas fragment transplantation has been investigated as a means for permanent insulin replacement (Lacy, 1995; Vajkoczy et al., 1995). Current methodologies use either cadaverous material or porcine islets as transplant substrates (Korbutt et al., 1997). However, significant problems to overcome are the low availability of donor tissue, the variability and low yield of islets obtained via dissociation, and the enzymatic and physical damage that may occur as a result of the isolation process (reviewed by Secchi et al., 1997; Sutherland et al., 1998). In addition are issues of immune rejection and current concerns with xenotransplantation using porcine islets.
It is clear that there remains a critical need to establish alternatives to the treatment of diabetes by self-injection of insulin. While stem cell research has shown promise in this regard, there has not been great success. There is a need for improved procedures for isolating, culturing, and transdifferentiating non-pancreatic cells to be used in the treatment of diabetes.